Processes for the preparation of 1,3-propane diol or trimethylene glycol (TMG) from glycerol are known. When performing these, essentially the following points must be taken into consideration. Bacterial strains able to convert glycerol into 1,3-propane diol are found e.g. in the species Klebsiella (cf. J. Bacteriol., 1982, 149, 413-419), Citrobacter (cf. J. Bacteriol., 1944, 39, 409-415), Clostridium (cf. Appl. Environ. Microbiol., 1987, 53, 639-643), Ilyobacter (cf. Arch. Microbiol., 1984, 140, 139-146) and Lactobacillus (cf. System. Appl. Microbiol., 1984, 5, 169-178). It cannot be excluded that further obligatory or optional ferments also form 1,3-propane diol as a fermentation product. Within the Citrobacter species, C. freundii is particularly well known as a 1,3-propane diol producer. Several strains (e.g. DSM 30039, 30040 and 30047) are available.
As a function of the bacterial strain used, it is possible to employ mineral media with glycerol or complex media with glycerol for the growth and associated production of 1,3-propane diol. The ambient conditions, such as the pH and temperature, are also dependent on the strain used. Preference is always given to anaerobic growth conditions, because the enzymes for the transformation of glycerol into 1,3-propane diol are only formed under anaerobic conditions. An adequate cobalt iron supply to the bacteria must be ensured, because the participating enzyme glycerol dehydratase contains coenzyme B.sub.12 (cf. Arch. Biochem. Biophys., 1962, 97, 538-543).
Using the aformentioned bacterial strains, 1,3-propane diol can be produced batchwise or continuously. As a function of the species, different 1,3-propane diol yields are obtained in the batchwise anaerobic fermentation of glycerol: 78% for Lactobacillus buchneri, 61% for Clostridium butylicum, 40% for Ilyobacter polytropus and 50% for Citrobacter freundii. In connection with the Lactobacillus species, it must be borne in mind that a mixture of glycerol and glucose (2:1) and not glycerol alone can be fermented. As a function of the bacterial species during the fermentation of glycerol different by-product spectra appear, mainly acetate, butyrate, lactate, formate, succinate, ethanol, butanol and hydroxypropionate (in the case of Ilyobacter polytropus).
Whereas the aforementioned fermentations relate to cultures operating in a batchwise manner, in 1987 results were published for the first time concerning a continuous fermentation of glycerol for the production of 1,3-propane diol (cf. Appl. Environ. Microbiol., 1987, vol. 53, 639-643). Fermentation was carried out with Clostridium butylicum B 593, an obligatory ferment. 3.8% glycerol were added to the chemically defined medium and 97% thereof were reacted by the bacteria. It was also necessary to add 0.2% yeast extract to the medium. In the gas phase there was oxygen-free carbon dioxide, the residence time of the bacteria in the reactor was 10 hours and the temperature 35.degree. C. Continuous fermentation gave the following product spectrum analyzed with HPLC and GC: 61% 1.3-propane diol, 6.6% acetate, 1.6% butyrate, 0.9% lactate, 0.6% butanol and 0.6% ethanol.
On the basis of the above statements, a 1,3-propane diol synthesis without by-products does not appear to be possible with bacteria, because part of the glycerol must be oxidized in order to obtain energy, whilst the reduction of glycerol to 1,3-propane diol is used for eliminating hydrogen which occurs. On lowering the pH-value from 6.5 to 4.9 the growth of bacteria and 1,3-propane diol production are reduced. An intermediate during the synthesis of 1,3-propane diol is 3-hydroxypropionaldehyde, whose production was also the aim of certain fermentation tests (cf. Appl. Environ. Microbiol., 1983, vol. 46, No. 1, 62-67). In the case of anaerobic fermentation of glycerol with Klebsiella pneumoniae, the speed of enzymatic reaction was displaced through the addition of semicarbazide hydrochloride. 3-hydroxypropionaldehyde production took place much more rapidly than the subsequent reduction to 1,3-propane diol and consequently led to a 3-hydroxypropionaldehyde accumulation. In the case of 30 g/l glycerol solutions, a 3-hydroxypropionaldehyde yield of 13.1 g/l was obtained.